Leptospirosis is a re-emerging infectious disease affectingboth animals and humans worldwide. This infection is associatedwith occupational contact with animals, recreational exposureand contact with leptospires as a consequence of flooding.Multiple organ involvement may be encountered in acutesevere leptospirosis and early renal involvement is commonlycharacterized by tubulo-interstitial nephritis and tubular dysfunction.Leptospirosis has been increasingly recognized as animportant infectious disease in Taiwan since 1997 andLeptospira santarosai serovar Shermani is the main serovarencountered. The most common presentations are fever, jaundiceand acute renal failure. This triad presentation in patientswith acute multiple organ dysfunction should alert physiciansto the possibility of leptospirosis. Penicillin treatment is effectiveand may dramatically save patients from multiple organfailure provided it is given early. The rapid IgM assay may aid screening of Leptospirosis,thus allowing effective treatment to be initiated early. Leptospirosis appears to be underestimatedin Taiwan and affects at least 10% of patients with multiple organ dysfunction.Therefore, a high level of clinical suspicion may help in identifying underestimated leptospirosisin Taiwan.